Method and arrangement for heating extended steel products

ABSTRACT

A method and apparatus for heating extended steel products, such as pipes, tape, or wire products or rods following working such as rolling or extrusion, to a heat treatment temperature, normally to approximately 50 to 900 degrees Celsius. The heating takes place as a result of the product being fed through a burner that has a central through channel into which the product is fed. Fuel and oxidant are supplied through channels that are outside of the central channel and are supplied at such a rate that the combustion of the fuel takes place in front of an outlet opening of the burner head of the burner.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and an arrangement for heating extended steel products.

2. Description of the Related Art

During working of steel products the mechanical, metallographic, and surface chemistry properties of the material change. It might be necessary to change those properties before further working and/or use. Heat treatment is one method of changing the properties of the material. Heat treatment involves the heating of the material to a certain temperature, followed by its subsequent cooling.

The rate of heating depends upon three factors, namely the supply of heat to the surface of the material, the heat transfer through the boundary layer to the surface of the material, and the conduction of heat within the material. The conduction of heat within the material is a material constant, and for that reason it cannot be influenced, whereas the supply of heat and the transfer of heat through the boundary layer remain as factors subject to influence.

One problem that arises during the heating of extended steel products is that the supply of heat energy should be even over the material surface of the product.

Another problem relates to the material surface of a product that is to be heated often having chemicals, such as roller oils, lubricating soap grease, rust protection oils, polymers, and organic and/or inorganic particles. Such contaminants may result in undesirable effects on the surface during heating or heat treatment, such as deposits on or in the heat treatment equipment, visual surface defects on the material, and/or an influence on the surface properties of the finished material.

The present invention solves those problems.

SUMMARY OF THE INVENTION

The present invention thus relates to a method for heating extended steel products, such as pipes, tape, or wire products or rods following working, such as by rolling or extrusion, to a heat treatment temperature, normally to approximately 50 to 900 degrees Celsius. The heating takes place by feeding the product through a burner that has a central through channel into which the product is fed. Fuel and oxidant are supplied through channels that exist outside of the central through channel and are supplied at such a rate that the combustion of the fuel takes place in front of the outlet opening of the burner head of the burner.

The invention also relates to an arrangement for carrying out the method.

BRIEF DESCRIPTION OF THE DRAWING

The invention is described in more detail below, partly in association with an embodiment of the invention shown in the attached drawing wherein

FIG. 1 shows a section through a burner in accordance with an embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to the heating of extended steel products, such as pipes, tape, or wire products or rods, following working, such as by rolling or extrusion, to a heat treatment temperature, normally to approximately 50 to 900 degrees Celsius.

According to the invention, the heating takes place by virtue of the product being fed through a burner. The burner has a central through channel into which the product is fed. Fuel and oxidant are supplied through existing channels located outside of the central channel. According to the invention, furthermore, fuel and oxidant are fed forward at such a rate that combustion takes place in front of the outlet opening of the burner head of the burner.

FIG. 1 shows an arrangement in the form of a burner 1 for the heating of extended steel products.

The burner 1 has a central through channel 2 arranged such that the product is fed along channel 2 and through the burner 1. The channel 2 is formed by a tube 3. Furthermore, channels 4, 5 are present in the burner 1 for the supply of fuel 6 and oxidant 7, respectively, and are located outside of the central channel 2. The channels 4, 5 for the supply of fuel and oxidant are, according to the invention, arranged such that combustion takes place in front of the outlet opening 13 of the burner head 12 of the burner 1.

In accordance with one preferred embodiment the extended material 9 to be heated is fed through the burner 1 in a direction that is opposite to the flow of the exhaust gases that result from combustion of the fuel.

The material 9 to be heated is fed through the burner 1 in the direction shown by arrow 10, while the exhaust gases flow in the direction shown by arrow 11. The combustion of the fuel thus takes place outside of the opening 13 of the head 12 of the burner 1.

It is preferred that fuel and oxidant are supplied from the burner head outlet opening at an angle of between 1 and 90 degrees to the longitudinal axis of the material 9.

According to one preferred embodiment, the combustion flame is formed inside of a flame tube 14 that extends outwardly of the outlet opening 13 of the burner 1 and is concentric with the transport pathway of the material 9.

By passing the material through the burner, it is ensured that the heat energy supplied is evenly distributed along the periphery of the extended steel product surface. There is a large heating intensity or heating power at the first point of contact between the material and the combustion flame, and that intensity decreases in a direction away from the outlet opening 13 of the burner, in a direction that is opposite to the direction of motion of the material. The power of the pre-heating before the direct impingement of the flame can be varied by adapting the length of the flame tube. It is the length of the flame tube that is varied. The combustion process can be made “flameless” by the recirculation of exhaust gases that takes place in the flame tube.

According to another preferred embodiment, oxidant and fuel are fed out from the outlet opening 13 of the burner 1 in a symmetrical manner with respect to the product.

Thus, it is preferred that oxidant and fuel are fed out from the outlet opening of the burner evenly distributed over the periphery of the product.

It is also preferred that the oxidant contains at least 85% oxygen by volume.

The heating time for heating the material in a heat treatment furnace is considerably shortened through the higher transfer of heat, which ensures that the rate of feed of the material through the heat treatment furnace can be considerably increased for a given heat treatment furnace.

Furthermore, the effect of at least one of the heat of combustion and the mechanical blowing away of deposits and oil residues, etc., is achieved by the direction of feed of the material being in a direction that is opposite to the flow of the exhaust gases. The surface will in that way become free of combustion products and other contaminants before further treatment of the material, such as, for example, heat treatment, working, removal of oxide, etc.

In a cross-section through a burner in accordance with the invention, it is divided into two halves along its longitudinal axis. One half can be displaced relative to the other half by means of a force-producing means. The construction of the burner in a divided form ensures the advantage that the extended steel product does not need to be threaded through the burner during the start-up procedure. 

1. A method for heating extended steel products, such as pipes, tape, or wire products or rods following working, such as rolling or extrusion, to a heat treatment temperature of approximately 50 to 900 degrees Celsius, said method comprising the steps of: feeding the extended steel product through a burner that has a central through channel into which the extended steel product is fed; and supplying fuel and oxidant through respective fuel and oxidant channels that are outside of the central through channel and at such a rate that combustion takes place in front of an outlet opening of a burner head of the burner and heat is distributed around the periphery of the extended steel product.
 2. A method according to claim 1, wherein the extended steel product is fed through the burner in a direction that is opposite to a direction of flow of burner exhaust gases.
 3. A method according to claim 1, wherein the oxidant and fuel are fed out from the outlet opening of the burner head around and in a symmetrical manner with respect to the extended steel product.
 4. A method according to claim 3, wherein the oxidant and fuel are fed out from the outlet opening of the burner head and are evenly distributed over the periphery of the extended steel product.
 5. A method according to claim 1, wherein the fuel and oxidant are supplied from the burner head outlet opening at an angle that lies between 1 and 90 degrees to a longitudinal axis of the extended steel product.
 6. A method according to claim 1, wherein the oxidant contains at least 85% oxygen by volume.
 7. A method according to claim 1, including the step of forming a flame within a flame tube that extends out from the outlet opening of the burner head and is concentric with a transport pathway of the extended steel product.
 8. An arrangement for heating extended steel products, such as pipes, tape, or wire products or rods following working, such as rolling or extrusion, to a heat treatment temperature of approximately 50 to 900 degrees Celsius, said heating arrangement comprising: a burner that has a central through channel arranged for the feed of the extended steel product through the burner; respective fuel and oxidant channels within the burner for the supply of fuel and oxidant, which fuel and oxidant channels are located outside of the central through channel; wherein the fuel and oxidant channels are positioned such that combustion takes place in front of an outlet opening of a burner head of the burner.
 9. A heating arrangement according to claim 8, wherein the extended steel product is fed through the burner in a direction that is opposite to a direction of flow of exhaust gases from the burner.
 10. A heating arrangement according to claim 8, wherein the outlet opening of the burner head is arranged to supply fuel and oxidant from the burner head outlet opening at an angle that lies between 1 and 90 degrees to a longitudinal axis of the extended steel product. 